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tcp: consolidate paws check

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Wow, it was quite tricky to merge that stream of negations
but I think I finally got it right:

check & replace_ts_recent:
(s32)(rcv_tsval - ts_recent) >= 0                  => 0
(s32)(ts_recent - rcv_tsval) <= 0                  => 0

discard:
(s32)(ts_recent - rcv_tsval)  > TCP_PAWS_WINDOW    => 1
(s32)(ts_recent - rcv_tsval) <= TCP_PAWS_WINDOW    => 0

I toggled the return values of tcp_paws_check around since
the old encoding added yet-another negation making tracking
of truth-values really complicated.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen
2009-03-14 14:23:03 +00:00
committed by David S. Miller
parent c43d558a51
commit c887e6d2d9
3 changed files with 21 additions and 12 deletions
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18
include/net/tcp.h
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@@ -997,11 +997,21 @@ static inline int tcp_fin_time(const struct sock *sk)
return fin_timeout;
}
static inline int tcp_paws_check(const struct tcp_options_received *rx_opt, int rst)
static inline int tcp_paws_check(const struct tcp_options_received *rx_opt,
int paws_win)
{
if ((s32)(rx_opt->rcv_tsval - rx_opt->ts_recent) >= 0)
return 0;
if (get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)
if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
return 1;
if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
return 1;
return 0;
}
static inline int tcp_paws_reject(const struct tcp_options_received *rx_opt,
int rst)
{
if (tcp_paws_check(rx_opt, 0))
return 0;
/* RST segments are not recommended to carry timestamp,